The subject matter disclosed herein relates to heat recovery steam generation systems and, in particular, to providing a multivariable algorithm to control multiple regulated outputs of a heat recovery generation system.
Heat recovery steam generators (HRSGs) recover heat from a gas stream and generate steam that is used in a turbine. In an HRSG, hot gas flows across an evaporator, which converts liquid water in the evaporator to steam. The steam is supplied to a steam drum, which supplies pressurized steam to a destination, such as a steam turbine. Operation of the HRSG is managed by monitoring and controlling flow of the liquid water, steam and heated gas in the HRSG. When one property of an HRSG is regulated to try to keep the property at a target value, the controlling of the property may affect one or more other regulated properties. For example, controlling a liquid water level in a steam drum may affect a steam pressure that is separately controlled. When the different properties are controlled with different control algorithms or processes, undesired changes in related properties of the HRSG may result, making it difficult to attain the desired target values for the various related properties.